submit: TxDescriptor<{
    update: {
        attested_header: {
            body_root: FixedSizeBinary<32>;
            parent_root: FixedSizeBinary<32>;
            proposer_index: bigint;
            slot: bigint;
            state_root: FixedSizeBinary<32>;
        };
        block_roots_branch: FixedSizeBinary<32>[];
        block_roots_root: FixedSizeBinary<32>;
        finality_branch: FixedSizeBinary<32>[];
        finalized_header: {
            body_root: FixedSizeBinary<32>;
            parent_root: FixedSizeBinary<32>;
            proposer_index: bigint;
            slot: bigint;
            state_root: FixedSizeBinary<32>;
        };
        next_sync_committee_update?: {
            next_sync_committee: {
                aggregate_pubkey: FixedSizeBinary<48>;
                pubkeys: FixedSizeArray<512, FixedSizeBinary<48>>;
            };
            next_sync_committee_branch: FixedSizeBinary<32>[];
        };
        signature_slot: bigint;
        sync_aggregate: {
            sync_committee_bits: FixedSizeBinary<64>;
            sync_committee_signature: FixedSizeBinary<96>;
        };
    };
}>

Submits a new finalized beacon header update. The update may contain the next sync committee.